Freeze warnings were issued for this morning across wide swaths of the L.A. Basin and San Diego County. Residents were being urged to cover outdoor plants and bring pets inside.

People in some parts of the Bay Area woke Saturday morning to something Saturday they're not quite accustomed to -- frost on their windshields.

The National Weather Service says temperatures in the aarea dropped into the upper 20s late Friday and early Saturday.

Forecasters say parts of the North Bay and East Bay saw some of the colder temperatures in the area, with the temperature in Angwin -- a tiny community in Napa County -- hitting a low of 23 degrees, while Clayton -- in Contra Costa County -- saw a low of 24 degrees.

In Southern California, morning frost was expected on San Diego and Los Angeles beaches. Big Sur, on the central coast, prepared for daytime highs almost 20 degrees below Boston's. Even the snowbird haven of Palm Springs saw temperatures hover around freezing at night. A low of 12 degrees was recorded in the snow-covered Big Bear mountain resort east of Los Angeles.

In addition, San Diego zookeepers turned up the heat for chimpanzees, tourists covered their hands on Hollywood walking tours, and some farmers broke out wind machines and took other steps to protect crops from freezing.

Traffic was flowing again on a major Southern California traffic artery that was severed for the second time in three days because of snow.

The Grapevine segment of Interstate 5 was reopened at 7:25 a.m. Saturday, about four hours after icy conditions forced the closure, the California Highway Patrol said. The key link between the Central Valley and Los Angeles was also shut for about 17 hours on Thursday, stranding hundreds of truckers and other motorists.

In Sonoma County, homeless shelters handed out extra warm clothes to protect people from frigid overnight temperatures.

Some customers drove more than an hour to buy firewood.

"It's crazy busy here," said Renea Teasdale, office manager at The Woodshed in Orange, south of Los Angeles.

Still, it was business as usual as much of the state contended with temperatures in the high 40s and low 50s.

"It's still sunny Southern California, and I'm going to work on my legs all year long," said Linda Zweig, a spokeswoman for the Del Mar Fairgrounds, which is hosting a 5-kilometer run north of San Diego today. The lifelong San Diego-area resident is prone to wearing two sweatshirts when the temperature drops but refuses to give up on shorts.

In the San Joaquin Valley, the heart of California's citrus production, growers prepared for another round of freezing temperatures early today after seeing little crop damage Thursday and Friday nights.

"Last night was not a problem, but tonight and Monday morning could have the potential to be pretty cold," Paul Story, director of grower service at California Citrus Mutual, said Saturday.

Farmers run wind machines and water to protect their fruit, which can raise the temperature in a grove by up to 4 degrees, Story said. Existing moisture, sporadic rain and cloud cover can also help keep in heat.